feat: add DeepSeek V3.1 model to Chutes AI provider

[roomote]

Summary

This PR attempts to address Issue #7294 by adding DeepSeek V3.1 to the Chutes AI provider dropdown. Feedback and guidance are welcome.

Changes

• Added deepseek-ai/DeepSeek-V3.1 to the ChutesModelId type union
• Added model configuration with 163840 context window and 32768 max tokens
• Added comprehensive test coverage for the new model

Testing

• ✅ All existing tests pass
• ✅ New test case added for DeepSeek V3.1 model
• ✅ Type checking passes
• ✅ Linting passes

Related Issue

Fixes #7294

Notes

The DeepSeek V3.1 model uses the same configuration parameters as DeepSeek V3, with the standard temperature (0.5) for non-R1 DeepSeek models.

---

Important

Add DeepSeek V3.1 model to Chutes AI provider with configuration and test coverage.

• Behavior:
  • Add deepseek-ai/DeepSeek-V3.1 to ChutesModelId in chutes.ts.
  • Configure DeepSeek V3.1 with 163840 context window and 32768 max tokens in chutes.ts.
  • Use standard temperature (0.5) for non-R1 DeepSeek models.
• Testing:
  • Add test case for DeepSeek V3.1 in chutes.spec.ts to verify model configuration.
  • Ensure all existing tests pass and add type checking and linting.

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[roomote]

Reviewing my own code. Found zero bugs. Suspicious.

[dmarkey]

https://openrouter.ai/deepseek/deepseek-chat-v3.1 according to here, Total Context is 163.8K

[daniel-lxs]

LGTM